Flow cytometry has become an important technique for rapid determination of cellular DNA content and for phenotype analysis of human tumors. Light scatter and fluorescence detection are used as two common parameters for flow cytometric analysis of human cells. For a variety of technical reasons, light scatter is of limited value in determining cellular volume as opposed to Electronic Coulter Volume measurement, which is a more reliable measure of volume. None of the commercially available flow cytometers can measure cellular volume. We have recently described the development and use of NASA/American Cancer Society flow cytometer capable of simultaneously measuring electronic nuclear volume (ENV) and DNA content of nuclei isolated from tumors. We have shown that by simultaneously measuring ENV vs. DNA content, we can discriminate between normal and tumor cells in a heterogeneous population and identify near-diploid (aneuploid) tumor cells. We believe this instrument can be used for monitoring the presence of tumor cells in body fluids such as ascites, pleural fluid, urine and in bladder washings. Specific aims of the present grant application are to: 1. Develop sample preparatory and staining methods for the analysis of cells from effusions, urine and bladder washings of patients with known or suspected malignancies. 2. Determine if simultaneous measurement of Electronic Nuclear Volume, DNA content and immunocytochemical marker expression can be used for rapid identification and detection of tumor cells in these liquid samples. 3. Compare data collected from flow cytometric analysis with that obtained from cytopathology and immunocytochemistry routinely performed on these specimens for diagnostic purpose.